This invention relates to a drive apparatus capable of applying a driving force on the micro- or nanometer order to a driven body. More particularly, the invention relates to a microdrive apparatus applicable to a working drive mechanism for a micromanipulator used in biotechnology, a positioning mechanism for effecting positioning between a manipulated object and a miniature instrument for manipulation, and a robot or articulated mechanism which undergoes fine movement.
An apparatus for effecting fine movement by means of impact force using a piezoelectric element (or an electrostrictive element) has previously been proposed by the inventor of the present application and has been disclosed as Japanese Patent Application Laid-Open (KOKAI) No. 63-299785.
The general features of the construction and operation of this conventional apparatus for effecting fine movement will now be described with reference to FIGS. 1 through 4.
The apparatus for effecting fine movement includes a moving member 2, an inertial member 3 and a piezoelectric/electrostrictive element 4 coupling the members 2 and 3 together, and is so adapted that the moving member 2 is placed on a base 1 and held there by frictional force.
By applying a voltage to the piezoelectric/electrostrictive element 4, the inertial member 3 is accelerated and the reaction thereof is utilized to cause movement of the moving member 2. This makes possible fine movement on the order of from 10 nm to 10 .mu.m through a simple mechanism.
The principle of movement is as follows: In a case where the moving member 2 is moved in the leftward (+) direction, as illustrated in FIG. 3, first the piezoelectric/electrostrictive element 4, which is in the constricted state shown in FIG. 3(a), is suddenly elongated, as illustrated in FIG. 3(b), the moving member 2 and inertial member 3 move away from each other. Next, when the piezoelectric/electrostrictive element 4 is slowly constricted, as shown in FIG. 3(c), and then suddenly stopped when it returns to its original length, as depicted in FIG. 3(d), the inertial member 3 subjects the moving member 2 to an impact. As a result, the moving member 2 is moved to the left, as shown in FIG. 3(e). In a case where the moving member 2 is moved in the rightward (-) direction, as illustrated in FIG. 4, first the piezoelectric/electrostrictive element 4, which is in the elongated state shown in FIG. 4(a), is suddenly constricted, as shown in FIG. 4(b). When this is done, the moving member 2 and inertial member 3 move toward each other. Next, as depicted in FIG. 4(c), when the piezoelectric/electrostrictive element 4 is slowly constricted, as shown in FIG. 4(c), and then suddenly stopped when it returns to its original length, as depicted in FIG. 4(d), the moving member 2 is moved to the right, as shown in FIG. 4(e).
Though a driven body can be moved (or rotated) in accordance with this prior art, considerable ingenuity is needed to utilize this art in a field of application that requires the microdrive control typical of micromanipulators.
In conventional micromanipulators which perform very fine operations, means relying upon hydraulic pressure, electromagnetic force or mechanical drive are utilized as work drive mechanisms for moving a fine glass needle relative to a cell and as positioning mechanisms for positioning a miniature instrument relative to an object to be manipulated. In the prior art, therefore, the work drive mechanisms and positioning mechanisms of these micromanipulators are large in size.
Furthermore, the comparatively coarse operation of the work drive mechanism of the micromanipulator, the fine operation of the miniature instrument for manipulation, and the operation of the positioning device for positioning between the object and the miniature instrument are controlled individually and by using separate drive systems. For this reason, the apparatus is not only large in size but complicated in structure as well.
In addition, these operations are in part dependent upon control by human intervention and therefore require a skilled operator for control.